Studies of the efficacy of local hyperthermia to modify growth and response to local gamma irradiation are being completed and analyzed. Tumor is studied as early generation isotransplants of mammary carcinoma. Data available demonstrate a powerful effect of hyperthermia (e.g. 43.5 degrees C x 60') started at 60 min after irradiation to reduce TCD50: 7060 rad (control) and 3770 rad (test). However, damage to normal tissue for a specified tumor control probability is not apparently reduced by any combined treatment thus far tested. In the investigation of recurrence time distribution following single dose irradiation to mammary carcinoma, an unexpected number of local recurrences are noted after 100 days. Local recurrence frequency following 6800 rads are 16% at 100 days, 27% at 200 days, 38% at 300 days, 44% at 400 days, and 59% at 500 days. The remaining 41 mice in this group will be observed for an estimated 300-400 more days. Histopathology will be reviewed on each of the recurrences (after 5000, 6000, 6500, 6800, 7100 rads). Efficacy of C parvum administration to modify response of fibrosarcoma or squamous cell carcinoma to fractionated irradiation is being assessed. As part of this project, role of site of tumor growth is under study (muscle of leg, skin of flank, subcutaneous tissue of flank, lung, urinary bladder). Further, the part played by macrophage in tumor graft rejection is being investigated.